Biotechnology

Single chamber air–cathode microbial fuel cells as biosensors for determination of biodegradable organics Abstract Objectives Single chamber air cathode microbial fuel cells (MFCs) were investigated with sodium-acetate and peptone as test substrates to assess the potential for application as biosensor to determine the concentration of biodegradable organics in water/wastewater samples. Results MFCs provided well-reproducible performance at high (> 2000 mg COD l−1—Chemical Oxygen Demand) acetate concentration values. Current in the cells proved to be steady from 25 to 35 °C, significant decrease was, however, revealed in the current below 20 °C. Direct calculation of non-toxic biodegradable substrate concentration in water/wastewater from the current in MFCs is possible only in the non-saturated substrate concentration range due to the Monod-like dependence of the current. This range was determined by a fitted and verified Monod-based kinetic model. Half saturation constant (KS) values were calculated at 30 °C applying different external resistance values (100 Ω, 600 Ω and 1000 Ω, respectively). In each case KS remained below 10 mg COD l−1. Conclusions Biosensors with this particular MFC design and operation are potentially applicable for detecting as low as 5 mg COD l−1 readily biodegradable substrates, and measuring the concentration of these substances up to ~ 50–70 mg COD l−1.

Mupirocin: applications and production Abstract Mupirocin is an antibiotic from monocarboxylic acid class used as antibacterial agent against methicillin-resistant Staphylococcus aureus (MRSA) and can be obtained as a mixture of four pseudomonic acids by Pseudomonas fluorescens biosynthesis. Nowadays improving antibiotics occupies an important place in the pharmaceutical industry as more and more resistant microorganisms are developing. Mupirocin is used to control the MRSA outbreaks, for infections of soft tissue or skin and for nasal decolonization. Due to its wide use without prescription, the microorganism's resistance to Mupirocin increased from up to 81%, thus becoming imperative its control or improvement. As the biotechnological production of Mupirocin has not been previously reviewed, in the present paper we summarize some consideration on the biochemical process for the production of pseudomonic acids (submerged fermentation and product recovery). Different strains of Pseudomonas, different culture medium and different conditions for the fermentation were analysed related to the antibiotics yield and the product recovery step is analysed in relation to the final purity. However, many challenges have to be overcome in order to obtain pseudomonic acid new versions with better properties related to antibacterial activity.

Chromatographic purification of recombinant human erythropoietin Abstract Recombinant human erythropoietin is a valuable therapeutic protein used in the treatment of several serious diseases. It exists in different isoforms and is produced by genetically modified mammalian cells such as Chinese hamster ovary or human embryonic kidney cells. As for other biopharmaceutical drugs, a key factor for its successful industrial production is to achieve a high degree of purity and to decrease the content of critical impurities to trace amounts. This goal is achieved in the separation sequence which substantial part is formed by chromatographic steps. Therefore, downstream processing forms an essential part of production costs. This review presents the overview of published separation sequences and, analyzes the use of different types of chromatographic media such as affinity, ion-exchange, reversed-phase, hydrophobic interaction, multimodal, and size-exclusion chromatography adsorbents. Their application is discussed with regard to their place in the purification stages generally denoted as capture, intermediate purification and polishing.

Biodesulfurization of diesel oil in oil–water two phase reaction system by Gordonia sp. SC-10 Abstract Objectives Different sulfur contents of diesel oils were used for biodesulfurization to study the desulfurization capacity of Gordonia sp. SC-10 in oil–water two-phase reaction system. Results Gordonia sp. SC-10 showed great properties in desulfurizing diesel oil with different sulfur contents. This bacterium could decrease sulfur contents in different diesel oils from 194.7 ± 3.7 to 30.4 ± 0.5 mg/l and from 3035.3 ± 23.8 to 1792.8 ± 48.9 mg/l, respectively. Furthermore, this bacterium could desulfurize broad range of organosulfur compounds and had strong desulfurization activity against alkylated DBTs. For low-sulfur diesel oil, sulfur could be removed from 10.2 ± 0.1 to 5.0 ± 0.1 mg/l. Conclusions The newly isolated bacteria Gordonia sp. SC-10 showed a good performance in desulfurizing diesel oils, and it might be a useful desulfurizing biocatalyst to enable the industrialized application of biodesulfurization process.

Preparation of high-quality sunflower seed protein with a new chlorogenic acid hydrolase from Aspergillus niger Abstract Objective To investigate the biochemical and enzymatic properties of chlorogenic acid hydrolase (ChlH) from Aspergillus niger SD14.721 and its applicability in sunflower seed protein processing. Results The ChlH with two identical subunits (97 kDa) was highly stable. Its optimal temperature and pH were determined as 60 °C and pH 7.0. The Km towards chlorogenic acid (CGA) was 1.85 μM. Based on its N-terminal sequence (AVDSVDAIFA), the purified ChlH appeared to be a new chlorogenic acid hydrolase. When applied in sunflower seed protein extraction, ChlH removed 99.13% of CGA in sunflower seed pastes, thus the colour of sunflower seed protein (SSP) changed from green to grey and its visual acceptance improved. Meanwhile, the solubility, water absorption capacity, and emulsification stability of SSP were increased 48.39%, 59.32% and 22.92%, respectively. Conclusions A new ChlH was obtained and its feasibility as a CGA-removal tool to obtain high quality SSP was demonstrated.

Production of 8 S - and 10 S -hydroxy polyunsaturated fatty acids by recombinant Escherichia coli cells expressing mouse arachidonate 8 S -lipoxygenase Abstract Objective To quantitatively hydroxylate 8S- and 10S-positions on polyunsaturated fatty acids by recombinant Escherichia coli cells expressing mouse arachidonate 8S-lipoxygenase (8S-LOX). Results Hydroxylated products gained from the conversion of arachidonic acid (20:4Δ5Z,8Z,11Z,14Z, AA), eicosapentanoic acid (20:5Δ5Z,8Z,11Z,14Z,17Z, EPA), and (22:6Δ4Z,7Z,10Z,13Z,16Z,19Z, DHA) by recombinant E. coli cells containing 8S-LOX from mouse were identified as 8S-hydroxy-5,9,11,14(Z,E,Z,Z)-eicosatetranoic acid (8S-HETE), 8S-hydroxy-5,9,11,14,17(Z,E,Z,Z,Z)-eicosapentanoic acid (8S-HEPE), and 10S-hydroxy-4,8,12,14,16,19(Z,E,Z,Z,Z,Z)-docosahexaenoic acid (10S-HDoHE), respectively. Under the optimal hydroxylation conditions of pH 7.5, 30 °C, 5% (v/v) ethanol, 15 g cells l−1, and 5 mM substrate, AA, EPA, and DHA were hydroxylated into 4.37 mM 8S-HETE, 3.77 mM 8S-HEPE, and 3.13 mM 10S-HDoHE for 60, 90, and 60 min, with 87, 75, and 63% molar conversions, respectively. Conclusion To the best of our knowledge, this is the first quantitatively biotechnological production of 8S-HETE, 8S-HEPE, and 10S-HDoHE.

Cloning, expression, and characterization of a novel nitrilase, PaCNit, from Pannonibacter carbonis Q4.6 Abstract Objective Identification of a heavy metal ion-stimulated nitrilase with broad-spectrum substrate specificity. Results A novel nitrilase, PaCNit, was identified from Pannonibacter carbonis Q4.6 and its enzymatic properties were investigated. The maximum activity of PaCNit was observed at 65 °C and pH 7.0. PaCNit showed broad substrate specificity towards aliphatic, aromatic, and heterocyclic nitriles, and was tolerant to different organic solvents. Remarkably, PaCNit activity was highly stimulated by metal ions, particularly by Ag+ and Hg2+. Conclusion PaCNit nitrilase has a broad range of substrate specificity and can be activated by heavy metal ions. This specific characteristic makes it have a great potential for industrial application.

Thermostable CITase from Thermoanaerobacter thermocopriae shows negative cooperativity Abstract Objective The biochemical properties of a putative thermostable cycloisomaltooligosaccharide (CI) glucanotransferase gene from Thermoanaerobacter thermocopriae were determined using a recombinant protein (TtCITase) expressed in Escherichia coli and purified to a single protein. Results The 171-kDa protein displayed maximum activity at pH 6.0, and enzyme activity was stable at pH 5.0–11.0. The optimal temperature was 60 °C in 1 h incubation, and thermal stability of the protein was 63% at 60 °C for 24 h. TtCITase produced CI-7 to CI-17, as well as CI-18, CI-19, and CI-20, which are relatively large CIs. Additionally, an unusual kinetic feature of TtCITase was its negative cooperative behavior in the dextran T2000 cleavage reaction. Conclusions Based on our results, TtCITase can be applied to produce relatively large CIs at high temperature.

Bacteriocin encapsulation for food and pharmaceutical applications: advances in the past 20 years Abstract The encapsulation of bacteriocins from lactic acid bacteria has involved several methods to protect them from unfavourable environmental conditions and incompatibilities. This review encompasses different methods for the encapsulation of bacteriocins and their applications in both food and pharmaceutical fields. Based on the bibliometric analysis of publications from well-reputed journals including different available patents during the period from 1996 to 2017, 135 articles and 60 patents were collected. Continent-wise contributions to the bacteriocins encapsulation research were carried out by America (52%), Asia (29%) and Europe (19%); with the United States of America, Brazil, Thailand and Italy the countries with major contributions. Till date, different methods proposed for encapsulation have been (i) Film coatings (50%), (ii) Liposomes (23%), (iii) Nanofibers (22%) and (iv) Nanoparticles (4%). Bacteriocins encapsulation methods frequently carried out in food protection (70%); while in the pharmaceutical field, 30% of the research was conducted on multi drug resistant therapy.

Mild heat stress limited the post-acidification caused by Lactobacillus rhamnosus hsryfm 1301 in fermented milk Abstract Objective Fermented milk is the optimal vehicle for delivering probiotic bacteria. However, the viable count of probiotic bacteria such as some lactic acid bacteria and the post-acidification of fermented milk are a contradiction. The objective of this study was to restrict the post-acidification of the fermented milk containing living Lactobacillus rhamnosus hsryfm 1301. Results Mild heat stress treatment (46 °C, 1 h) was chosen to help control the post-acidification caused by L. rhamnosus hsryfm 1301. When fermented milk was produced by single L. rhamnosus hsryfm 1301, the heat stress treatment reduced the post-acidification from 0.39 to 0.11% lactic acid, and the viable cells were maintained above 2.0 × 108 CFU mL−1 during 21 days of storage. Although the post-acidification limitation of heat treatment was relatively weak in fermented milk produced by L. rhamnosus hsryfm 1301 and S. thermophilus grx02 (from 0.26 to 0.10% lactic acid), this treatment was still effective. Furthermore, no whey separation in the fermented milk was caused by the treatment. Conclusions Mild heat stress treatment could limit the post-acidification caused by L. rhamnosus hsryfm 1301 by decreasing its metabolism and proliferation. This treatment is a promising strategy to improve the shelf life of probiotic fermented milk.